Can I Say Something Bad?

We were trying to get the girls ready for bed Halloween night, but things weren't going well. They didn't want to get ready. They were so upset about Oreo's injury. They just wanted to talk about what happened.
The brunette twin was standing in the bathroom when she said, "Can I say something bad?"
I said, "Sure baby."
She said, "I hate those stupid, f*!*!ing people."
I was going to say that we don't call people stupid when the rest of her statement sunk in. I said, "Excuse me? Where do you hear talk like that?"
She replied, "Uncle Dave talks like that all the time."
Sigh...
We all have moments where we have potty mouths on my side of the family. I don't swear a lot, but when I'm overtired or frustrated or annoyed or mad I can throw in a few choice words. I realize it's the sign of a simple mind. Some days it's just an easy way to express myself. I don't do it in front of the girls though. I'm careful about that.
I call it channeling my inner-Dad. My father always swore. I think he probably started because it annoyed my Grandmother so much. After a while it just stuck.
We learned to swear with Dad at a young age. I always tell the stories about watching hockey with Dad. He would get so mad he'd swear at the TV. If Mom was in another room she'd say, "What happened?" We'd reply something like "a))hole missed the shot." We were little. We didn't know what we were saying. We were just repeating what Dad said.
As we got older we learned to distinguish between things Dad said and things we should say. I'm not saying we never said any bad words. We just made sure not to get caught by Mom. 
Now it's my brother Dave's turn to carry on the family tradition. I explained to the brunette twin that while Uncle Dave might say certain things it was never okay for her to repeat them. She said, "I know Mom that's why I asked if I could say something bad." Seems that she knows the lesson and how to get around it. Turns out I need to think a bit more before I answer her questions from now on.